Wingtip devices modify the airflow around an aircraft's wingtip to improve the aerodynamic efficiency of the wing. Wingtip devices can improve the aerodynamic capabilities of an aircraft by reducing the effect of wingtip vortices. Wingtip vortices are created when high pressure air below the wing migrates around the wingtip to the low pressure regions above the wing. This phenomenon causes high speed, low pressure regions of rotational flow around the wingtip that drains energy from the aircraft in the form of induced drag. Conventional wingtips produce strong vortices that can account for more than half of aircraft drag in cruise flight and even more in other flight conditions.
Aircraft wings can be modified to try to improve performance. One wingtip device is a winglet. Winglets are configured as near-vertical airfoils and positioned at each end of an aircraft's standard wingtip. Winglets may be configured in an up, down, or up and down configuration, or they may be blended into a wing. If properly designed, winglets can reduce the strength of wingtip vortices and thereby reduce induced drag.
Another wingtip device is a raked wingtip. Raked wingtips are positioned near the tip of the wing. Raked wingtips provide an area of localized increase in wing sweep. If properly designed, they can improve aircraft performance by increasing a wing's aspect ratio and reducing the wingtip chord. Although raked wingtips reduce drag, they increase the weight of the wing so any reduction in drag must be balanced against the increased weight of the wing. They do not create interference drag because they are in the same plane as the wing, but they generally add more moment to a wing than winglets. In addition, raked wingtips increase wing span, which presents challenges for ground handling, parking, and hanger storage.
Other wingtip devices include wing tip fences, planar wing extensions, blended winglets, and spiroids. These devices are mounted in the region of the wingtip. Although these wingtip devices can reduce the strength of wingtip vortexes and drag, further improvements are needed to improve fuel efficiency and aircraft performance.